[Proposal] Smartweave plugins

[andreespirela]

Hey there, this is Andres from Verto.exchange.

Overview:
Plugins are a way to introduced custom Javascript functions to the execution of smart weave contracts.

Details:
Plugins should be passed in a static call to a setter, for example:

import { setPlugins } from "smartweave";

setPlugins({
   helloWorld: () => console.log("hello world");
});

Or they can be passed in the readContract function.

export declare function readContract(arweave: Arweave, contractId: string, height?: number, returnValidity?: boolean, plugins?: any): Promise<any>

import { readContract } from "smartweave";

readContract(arweaveClient,
            contractId,
            undefined,
            true,
            {
                helloWorld: () => console.log("hello world");
            }
);

Accessing plugins
In order to access the plugins inside the contract, we can do:

SmartWeave.plugins[plugin_name]();

where SmartWeave is the global that all contract has, with a new object, which is call plugins, and contains the functions we passed in our object

SmartWeave.plugins['helloWorld']();

Security Flaws
A contract can override, or modify the plugins object. For this reason, this object should be frozen, and all its properties should also be frozen. A deep Object.freeze if you may.

@t8